Which of the following gases on dissolution in water make the solution acidic?

Options

A. CO
B. `CO_(2)`
C. `SO_(3)`
D. `PH_(3)`

Answer

To determine which gases make the solution acidic upon dissolution in water, we need to analyze each gas provided in the options. Here’s a step-by-step solution:

### Step 1: Identify the Gases
We will consider the following gases:
1. CO (Carbon monoxide)
2. CO2 (Carbon dioxide)
3. SO3 (Sulfur trioxide)
4. PH3 (Phosphine)

### Step 2: Analyze Each Gas

**Gas 1: CO (Carbon monoxide)**
- CO is a neutral oxide.
- When CO dissolves in water, it does not react to form any acidic solution.
- **Conclusion:** CO does not make the solution acidic.

**Gas 2: CO2 (Carbon dioxide)**
- CO2 is an acidic oxide.
- When CO2 dissolves in water, it reacts to form carbonic acid (H2CO3):
\[ \text{CO}_2 + \text{H}_2\text{O} \rightarrow \text{H}_2\text{CO}_3 \]
- Carbonic acid is a weak acid, which makes the solution acidic.
- **Conclusion:** CO2 makes the solution acidic.

**Gas 3: SO3 (Sulfur trioxide)**
- SO3 is also an acidic oxide.
- When SO3 dissolves in water, it reacts to form sulfuric acid (H2SO4):
\[ \text{SO}_3 + \text{H}_2\text{O} \rightarrow \text{H}_2\text{SO}_4 \]
- Sulfuric acid is a strong acid, which significantly lowers the pH of the solution.
- **Conclusion:** SO3 makes the solution acidic.

**Gas 4: PH3 (Phosphine)**
- PH3 is a neutral gas and does not react with water to form an acid.
- When PH3 is dissolved in water, no significant reaction occurs to produce an acidic solution.
- **Conclusion:** PH3 does not make the solution acidic.

### Step 3: Final Conclusion
Based on the analysis:
- The gases that make the solution acidic upon dissolution in water are:
- CO2 (Carbon dioxide)
- SO3 (Sulfur trioxide)

### Summary of Answers
- **Correct Options:** CO2 and SO3